For over 50 years, automotive engineers have been experimenting with acoustic drivers acting upon the intake charge of an internal combustion engine to solve a variety of problems. An example of such early work are a pair of patents, U.S. Pat. No. 2,414,494 (Vang) and U.S. Pat. No. 2,454,900 (Bodine). The preceding patents illustrate a series of devices located in the induction system or alternatively, within the confines of the combustion chamber to excite the air fuel mixture at sonic or supersonic frequencies, for the purposes atomizing the air fuel mixture. Substantially concurrently with the work of a William Hancock, U.S. Pat. No. 2,436,570, relating to the use of high frequency pressure pulsations in the intake charge to suppress detonation, Hancock suggested the use of in-chamber as well as intake manifold mounted diagram type vibrating actuators for exciting the intake charge in order to create high frequency pressure pulsations with the cylinder.
Approximately 10 years after the early work of Vang and Hancock, Ebhardt Hundt of Daimler-Benz, obtained a U.S. Pat. No. 2,737,163 relating to a vibrating driver to be mounted directly within the combustion chamber for ultrasonically exciting the intake charge. The driver had a specific structure designed to withstand the pressure and thermal loads resulting from its direct location in the combustion chamber. The Hundt device operated at frequencies up to 20 hertz that was intended to atomize fuel droplets prior to the completion of the compression stroke.
As an alternative to exciting the inner fuel mixture using a diaphragm type actuator. U.S. Pat. No. 2,949,900 of Albert Bodine disclosed a direct in the chamber injector which sonically pulsated the injected fuel at 5,000 to 50,000 cycles per second in order to improve fuel atomization.